Merge pull request #20866 from jdantonio/countdown-latch

Replace `ActiveSupport::Concurrency::Latch` with `Concurrent::CountDownLatch` from concurrent-ruby.

3 files changed, 14 insertions, 16 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 334eebc268..17c2f0eb27 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,8 @@
+*   Removed `ActiveSupport::Concurrency::Latch`, superseded by `Concurrent::CountDownLatch`
+    from the concurrent-ruby gem.
+
+    *Jerry D'Antonio*
+
 *   Fix not calling `#default` on `HashWithIndifferentAccess#to_hash` when only
     `default_proc` is set, which could raise.
 
diff --git a/activesupport/activesupport.gemspec b/activesupport/activesupport.gemspec
index 12c6a4d449..c18c1c87c9 100644
--- a/activesupport/activesupport.gemspec
+++ b/activesupport/activesupport.gemspec
@@ -25,4 +25,5 @@ Gem::Specification.new do |s|
   s.add_dependency 'tzinfo',     '~> 1.1'
   s.add_dependency 'minitest',   '~> 5.1'
   s.add_dependency 'thread_safe','~> 0.3', '>= 0.3.4'
+  s.add_dependency 'concurrent-ruby', '~> 0.9.0'
 end
diff --git a/activesupport/lib/active_support/concurrency/latch.rb b/activesupport/lib/active_support/concurrency/latch.rb
index 1507de433e..7b8df0df04 100644
--- a/activesupport/lib/active_support/concurrency/latch.rb
+++ b/activesupport/lib/active_support/concurrency/latch.rb
@@ -1,26 +1,18 @@
-require 'thread'
-require 'monitor'
+require 'concurrent/atomics'
 
 module ActiveSupport
   module Concurrency
-    class Latch
-      def initialize(count = 1)
-        @count = count
-        @lock = Monitor.new
-        @cv = @lock.new_cond
-      end
+    class Latch < Concurrent::CountDownLatch
 
-      def release
-        @lock.synchronize do
-          @count -= 1 if @count > 0
-          @cv.broadcast if @count.zero?
-        end
+      def initialize(count = 1)
+        ActiveSupport::Deprecation.warn("ActiveSupport::Concurrency::Latch is deprecated. Please use Concurrent::CountDownLatch instead.")
+        super(count)
       end
+      
+      alias_method :release, :count_down
 
       def await
-        @lock.synchronize do
-          @cv.wait_while { @count > 0 }
-        end
+        wait(nil)
       end
     end
   end